Synchronised will need to rewrite the history books if he is to give Tony McCoy a second Grand National winner in three years.

Unibet are to refund all losing outright win bets on the 2012 Grand National up to £30, Synchronised will also have to put up an astonishing weight-carrying performance.

Owned and trained by J P McManus and Jonjo O’Neill, who provided McCoy with Don’t Push It, the horse that fulfilled his Grand National dream in 2010, Synchronised is bidding to do something only the legendary Golden Miller has ever achieved.

Golden Miller, winner of five Cheltenham Gold Cups between 1932 and 1936, is the only horse ever to have captured steeplechasing’s Blue Riband and also the Grand National in the same year, 1934.

Many have tried and failed. Since 1977, Davy Lad, Alverton, Garrison Savannah, Cool Ground, The Fellow and, most recently in 1995, Master Oats have fallen short in the quest for the historic double.

Garrison Savannah went closest in 1991 when he was caught on the run-in by Seagram having looked certain to score for Jenny Pitman.

The nine-year-old must carry 11st 10lbs at Aintree, a burden that has not been defied since the great Red Rum shouldered 12st to victory in the second of his three Grand National triumphs in 1974.

Before that, you have to go back to Freebooter in 1950 who carried 11st 11lbs.

And it is not just history and the weight that is siding against Synchronised. There is also the fact that this year’s Grand National looks as competitive as any in memory, with so many more good-quality horses lining up these days as opposed to the host of no-hopers that regularly featured up until the last decade or so.

However, Synchronised is the favourite for a good reason, which is that he has the best form having beaten the top chasers around to win the Cheltenham Gold Cup.

Yes, he endured a hard race that day, being off the bridle for much of the contest and McCoy will know he will not have it easy for the 10 minutes of the Grand National.

But the champion jockey, with his never-say-die spirit, is capable of winning races that his colleagues physically cannot.

If anyone can bring Synchronised home in front to rewrite the record books, Tony McCoy is that man.